Ecohydrological water flow analysis of a Swedish landscape in a 100 year perspective

Andersson, Lotta

Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.

1989 (English)Doctoral thesis, comprehensive summary (Other academic)

Abstract [en]

The study basically involves analysis in a 100 year perspective of the hydrological response on precipitation from different landscape elements in south-central Sweden, characterized by the interaction of topography, soil type, land management and canopy cover.

For this purpose, a dynamic water partitioning model, based on the soil moisture balance, was developed together with a Geographical Information System (GIS)-supported method for the detection of the spatial distribution of soil wetness as an indicator of the probability to act as discharge or recharge areas respectively.

A comparison was made of the performance of water balance models of various complexity. It was shown that, generally, increasing the complexity of the submodels did not improve the agreement with measured soil moisture dynamics. As an example, due to negative feedbacks, the rather conservative nature of transpiration was well described by using 30 years monthly means of potential evapotranspiration. However, two important physical processes that are often neglected in water balance models had to be included: the limitation of transpiration by low soil and air temperatures in spring and early summer, and the drainage of rainwater through unsaturated forest soils.

The model was used to analyze main differences in hydrological response between forests and open grasslands. It was also used to analyze interannual fluctuations of soil moisture deficts. Ironically, the variability was never as high as in the beginning of the hydrological year. The study revealed considerable fluctuations of 10, 30 and 50-year mean soil moisture deficits, and a general secular trend towards higher summer deficits and larger fluctuations around the median. In the light of the detected critical importance of the choice of time period, the concepts of return and standard periods were challenged. It was shown that the water balance model could be calibrated to simulate also overall basin response. Thus, simulated monthly estimates of both basin evapotranspiration and recharge rates for the Velen Representative Basin agreed well with data determined with other methods.

The model was also used to simulate the integrated basin response from different parts of the landscape mosaic as determined from GIS-overlays. The obvious advantage of GIS was demonstrated. Finally, changes due to the wetness-impacting human interventions were analyzed. Since the 1870s such activities were shown to, on average, have caused a slight desiccation of the landscape, although the impacts locally could be large.

Public defence

Note

Papers, included in the Ph.D. thesis, are not registered and included in the posts from 1999 and backwards.Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2018-01-13Bibliographically approved